Question: Which of these numbers is prime? ${10,\ 69,\ 73,\ 93,\ 99}$
A prime number has exactly two factors: 1 and itself. The factors of 10 are 1, 2, 5, and 10. The factors of 69 are 1, 3, 23, and 69. The factors of 73 are 1 and 73. The factors of 93 are 1, 3, 31, and 93. The factors of 99 are 1, 3, 9, 11, 33, and 99. Thus, 73 is a prime number.